Why CDNs will not always improve your SEO

There are few industries that evolve with quite the same regularity as SEO.The ongoing changes to Google’s algorithm have meant that many people employed in the sector are carrying out completely different tasks from five years ago, despite often having the same job title!

Indeed, in the past year alone, Google has made a number of key changes to the way it works. Some of the changes include making organic search data completely secure, apparently stopping PageRank updates, and increasing the emphasis on its own social network, Google+.SEOs have continually had to evolve their methods to try and keep up, with new things being discovered every month.One survey in particular showed that considerations are constantly changing, in exploring the connection between TTFB and search success.

About TTFB

The above survey obviously provides some key data, but it’s tricky to understand without further exploring TTFB itself.

TTFB, or Time to First Byte as its full name goes, is the metric used to measure how long it takes a website to send the first byte of response from the server back to the user.Essentially, it’s another method of measuring how fast a website can start loading within your browser. In more technical terms, TTFB is the time it takes to initiate browser-side parsing, which is a process in which the HTML content is rendered and put on screen.

Can Your CDN Cache Dynamic HTML?

Recently, an interesting study (also available as an infographic) by the networking experts at Incapsula highlighted an important link between CDNS technology (Content Delivery Networks) and the TTFB metric.Surprisingly enough, it’s not the positive connection most might expect.

The reason itself is fairly simple.Today, most modern websites rely heavily on dynamically-created HTML pages.Such dynamically generated HTML object are ignored by 9 out of 10 CDNs, which are only designed to accelerate static website resources (e.g., images) As a result, in all such cases, CDNS actually won’t have a positive impact on the website’s TTFB and will even slow it down, by adding an additional connection point between the HTML content and the website’s visitor.

Incapsula research continues to show how, due their dynamic origin, HTML objects are often cause delivery bottlenecks. In fact, after inspecting over 1 Billion sessions, Incapsula researches saw that – in terms of overall delivery time – such typically “light” HTML resources are actually 10 times slower than the much heavy images.

That may sound counter-intuitive, but these numbers actually make a lot of sense when you consider that, with modern +100Mbps networks, the actual file size is almost irrelevant to the actual load time and user-experience.

And so, as Incapsula’s article points out, today most of the lag comes from the time it takes to generate the content on the server, rather than the time it takes to deliver it to the visitor.

This is why, when you look at HTML files in your browser console, you will usually see that most of the time is spend on Waiting rather than on Receiving. And so, 99% of the time you just wait – wait for the server to finish putting together the dynamically generated HTML content.

So how can CDNs Really Improve Your SEO?

Assuming that TTFB is really as crucial as the Moz study concludes, then most CDNs will not provide any major SEO benefits.However, some of the modern content delivery networks have evolved beyond their basic bare-bone capabilities.Today, such CDNs are able to cache dynamically rendered HTML content, either by manually overriding the default caching rules or – better yet – by intelligently optimizing caching predicates and automatically caching dynamic HTML objects.

In both cases, and especially in the latter scenario, CDNs can actually provide significant SEO benefits, simply by removing all need for server processing and by doing so taking the Waiting time out of your TTFB equation.